The present invention relates to new dentifrice compositions having anti-caries activity and containing a polycationic polymer fluoride.
In the following description, "dentifrice composition" is used to mean any solid or liquid composition intended for mouth hygiene, such as toothpaste, chewing gum, powder or mouthwash.
It is known that the use of products for cleaning teeth, and in particular dentifrice compositions, has for an essential object, insofar as the prevention of caries is concerned, the removal of dental plaque or the prevention of its formation. Dental plaque, which is composed of food residues transformed by bacterial metabolism, is a deposit which hardens and strongly adheres to the teeth if it is not rapidly removed. Dental plaque in turn promotes the multiplication of bacteria which transform sugars into acid products. These acid products attack tooth enamel and demineralize it. In the absence of treatment, the bacteria and their acid secretions can progressively reach the tooth pulp, going so far as to cause its destruction.
It is also known that dental plaque deposited on teeth and gums where they contact same plays an important role in various gum infections.
It is known that conventional dentifrice products which principally contain abrasive particles (polishing agents) and surface active agents (cleaning and foaming agents) do not provide sufficient removal of dental plaque and the prevention of caries.
In order to fight more effectively against caries, various bactericidal products capable of destroying or limiting to a great extent the populations of bacteria responsible for the formation of dental plaque have been proposed.
It must, however, be noted that the use of bactericidal agents poses formulation problems, since it is necessary to find bactericidal agents which are compatible both with the abrasive agent and with the surface active agent. These formulation difficulties are sufficiently great to have led researchers to recommend the successive use of two separate compositions, one containing the surface active agent and the other containing the bactericidal agent; see French Patent Application No. 75.26219 published under No. 2,282,861.
The prevention of caries has also been researched by attempting to use to advantage the properties of fluoride ions which are used in a small amount. It is generally agreed that fluoride ions have the effect of transforming the hydroxyapatite of tooth enamel into fluoroapatite, which increases the crystallinity and the hardness of the enamel and thus renders it more resistant to acid attack.
The use of metal fluorides, such as sodium fluoride and tin fluoride, in dentifrice compositions, has also been recommended. However, these fluorides have the disadvantage of low compatibility with conventional mineral polishing agents, in particular with alumina and calcium carbonate, contained in toothpastes, with the interactions between said fluorides and the polishing agents leading in particular to a decrease in the content of free fluoride ions and, therefore, to lower effectiveness.
In order to overcome these disadvantages, the use of monofluorophosphate, which is more compatible with polishing agents, has been proposed. However, even with the use of dentifrice products containing high amounts of fluorophosphate, the fixation of the fluoride ions onto the teeth remains fairly low due to the limited contact time between the dentifrice composition and the tooth.
However, monofluorophosphate does not act directly on the primary cause of caries, i.e., bacteria. This is the reason for which, with a view to increasing the effectiveness of the fluoride ions, anti-bacterial, anti-plaque agents have often been added to them.
It has also been proposed to apply on the teeth fluid materials, which are capable of hardening rapidly, so as to form a protective resin coating which can play the role of fluoride ion exchanger. However, such hardenable fluid compositions can, in practice, only be used on teeth which are already affected with caries and cannot be used for normal hygienic care in dentifrice compositions. In addition, the need to apply a non-hardened composition has various disadvantages due, in particular, to the toxicity of the monomer compounds and possibly of the polymerization initiators whose presence is necessary; see the article by B.R. Rawls and P.P. Zimmerman, Caries Res. 17:32-43 (1983).